diff options
Diffstat (limited to 'drivers/pps/clients/pps_parport.c')
| -rw-r--r-- | drivers/pps/clients/pps_parport.c | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c new file mode 100644 index 000000000000..32221efd9ca9 --- /dev/null +++ b/drivers/pps/clients/pps_parport.c @@ -0,0 +1,258 @@ +/* + * pps_parport.c -- kernel parallel port PPS client + * + * + * Copyright (C) 2009 Alexander Gordeev <lasaine@lvk.cs.msu.su> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + + +/* + * TODO: + * implement echo over SEL pin + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/irqnr.h> +#include <linux/time.h> +#include <linux/parport.h> +#include <linux/pps_kernel.h> + +#define DRVDESC "parallel port PPS client" + +/* module parameters */ + +#define CLEAR_WAIT_MAX 100 +#define CLEAR_WAIT_MAX_ERRORS 5 + +static unsigned int clear_wait = 100; +MODULE_PARM_DESC(clear_wait, + "Maximum number of port reads when polling for signal clear," + " zero turns clear edge capture off entirely"); +module_param(clear_wait, uint, 0); + + +/* internal per port structure */ +struct pps_client_pp { + struct pardevice *pardev; /* parport device */ + struct pps_device *pps; /* PPS device */ + unsigned int cw; /* port clear timeout */ + unsigned int cw_err; /* number of timeouts */ +}; + +static inline int signal_is_set(struct parport *port) +{ + return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0; +} + +/* parport interrupt handler */ +static void parport_irq(void *handle) +{ + struct pps_event_time ts_assert, ts_clear; + struct pps_client_pp *dev = handle; + struct parport *port = dev->pardev->port; + unsigned int i; + unsigned long flags; + + /* first of all we get the time stamp... */ + pps_get_ts(&ts_assert); + + if (dev->cw == 0) + /* clear edge capture disabled */ + goto out_assert; + + /* try capture the clear edge */ + + /* We have to disable interrupts here. The idea is to prevent + * other interrupts on the same processor to introduce random + * lags while polling the port. Reading from IO port is known + * to take approximately 1us while other interrupt handlers can + * take much more potentially. + * + * Interrupts won't be disabled for a long time because the + * number of polls is limited by clear_wait parameter which is + * kept rather low. So it should never be an issue. + */ + local_irq_save(flags); + /* check the signal (no signal means the pulse is lost this time) */ + if (!signal_is_set(port)) { + local_irq_restore(flags); + dev_err(dev->pps->dev, "lost the signal\n"); + goto out_assert; + } + + /* poll the port until the signal is unset */ + for (i = dev->cw; i; i--) + if (!signal_is_set(port)) { + pps_get_ts(&ts_clear); + local_irq_restore(flags); + dev->cw_err = 0; + goto out_both; + } + local_irq_restore(flags); + + /* timeout */ + dev->cw_err++; + if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) { + dev_err(dev->pps->dev, "disabled clear edge capture after %d" + " timeouts\n", dev->cw_err); + dev->cw = 0; + dev->cw_err = 0; + } + +out_assert: + /* fire assert event */ + pps_event(dev->pps, &ts_assert, + PPS_CAPTUREASSERT, NULL); + return; + +out_both: + /* fire assert event */ + pps_event(dev->pps, &ts_assert, + PPS_CAPTUREASSERT, NULL); + /* fire clear event */ + pps_event(dev->pps, &ts_clear, + PPS_CAPTURECLEAR, NULL); + return; +} + +/* the PPS echo function */ +static void pps_echo(struct pps_device *pps, int event, void *data) +{ + dev_info(pps->dev, "echo %s %s\n", + event & PPS_CAPTUREASSERT ? "assert" : "", + event & PPS_CAPTURECLEAR ? "clear" : ""); +} + +static void parport_attach(struct parport *port) +{ + struct pps_client_pp *device; + struct pps_source_info info = { + .name = KBUILD_MODNAME, + .path = "", + .mode = PPS_CAPTUREBOTH | \ + PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \ + PPS_ECHOASSERT | PPS_ECHOCLEAR | \ + PPS_CANWAIT | PPS_TSFMT_TSPEC, + .echo = pps_echo, + .owner = THIS_MODULE, + .dev = NULL + }; + + device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL); + if (!device) { + pr_err("memory allocation failed, not attaching\n"); + return; + } + + device->pardev = parport_register_device(port, KBUILD_MODNAME, + NULL, NULL, parport_irq, 0, device); + if (!device->pardev) { + pr_err("couldn't register with %s\n", port->name); + goto err_free; + } + + if (parport_claim_or_block(device->pardev) < 0) { + pr_err("couldn't claim %s\n", port->name); + goto err_unregister_dev; + } + + device->pps = pps_register_source(&info, + PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR); + if (device->pps == NULL) { + pr_err("couldn't register PPS source\n"); + goto err_release_dev; + } + + device->cw = clear_wait; + + port->ops->enable_irq(port); + + pr_info("attached to %s\n", port->name); + + return; + +err_release_dev: + parport_release(device->pardev); +err_unregister_dev: + parport_unregister_device(device->pardev); +err_free: + kfree(device); +} + +static void parport_detach(struct parport *port) +{ + struct pardevice *pardev = port->cad; + struct pps_client_pp *device; + + /* FIXME: oooh, this is ugly! */ + if (strcmp(pardev->name, KBUILD_MODNAME)) + /* not our port */ + return; + + device = pardev->private; + + port->ops->disable_irq(port); + pps_unregister_source(device->pps); + parport_release(pardev); + parport_unregister_device(pardev); + kfree(device); +} + +static struct parport_driver pps_parport_driver = { + .name = KBUILD_MODNAME, + .attach = parport_attach, + .detach = parport_detach, +}; + +/* module staff */ + +static int __init pps_parport_init(void) +{ + int ret; + + pr_info(DRVDESC "\n"); + + if (clear_wait > CLEAR_WAIT_MAX) { + pr_err("clear_wait value should be not greater" + " then %d\n", CLEAR_WAIT_MAX); + return -EINVAL; + } + + ret = parport_register_driver(&pps_parport_driver); + if (ret) { + pr_err("unable to register with parport\n"); + return ret; + } + + return 0; +} + +static void __exit pps_parport_exit(void) +{ + parport_unregister_driver(&pps_parport_driver); +} + +module_init(pps_parport_init); +module_exit(pps_parport_exit); + +MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>"); +MODULE_DESCRIPTION(DRVDESC); +MODULE_LICENSE("GPL"); |